摘要:

The propagation of wave packets in a dispersive and anisotropic medium is formulated generally. An amplitude function is found to be a crucial auxiliary function that describes the three-dimensional propagation of a wave packet. This amplitude function, satisfying a differential equation, contains competing processes of dispersion and anisotropy in distorting the pulse. Once found, it must be further manipulated to obtain the field vector. As examples, this formulation is applied to propagation of two kinds of waves; gravity waves in a rotating atmosphere and electromagnetic waves in a magnetoplasma. Contrasting from the monochromatic case, the polychromatic features in the propagation of wave packets are pointed out both in polarization properties and amplitude dispersion.

ISSN:0920-5071    

DOI:10.1163/156939391X00013

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper presents a variational formulation for a rectangular slot coupled junction between two dissimilar rectangular waveguides with collinear axes. Equivalent network of this two-port junction is determined, taking the effect of thickness of the transverse metallic wall into account. Numerical results on normalized shunt admittance and complex reflection coefficient are presented for a junction between WR-90 and WR-112 rectangular waveguides, as a function of the slot width. A comparison between the theoretical and experimental results is presented for the limiting case when the two waveguides are identical.

ISSN:0920-5071    

DOI:10.1163/156939391X00022

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In this paper, a rigorous method for the analysis of the propagation characteristics of various rectangular waveguides is proposed based on the recent development of the numerical mode matching method for multi-region, vertically stratified media. Unlike the conventional two-dimensional finite element method which is widely used for the analysis of dielectric waveguide problems, the numerical mode matching method proposed in this paper uses the propagation properties of the waves on the cross-section of the waveguides to convert the two-dimensional problem into a few one-dimensional problems. These one-dimensional problems are then solved with the one-dimensional finite element method, resulting in a great saving of the number of unknowns needed. A major difference between this method and the conventional mode matching method is that the eigenvalues and eigenmodes of the constituent layered media are found numerically by using a one-dimensional finite element method, which makes the method more versatile than the conventional mode matching method. This analysis method has been implemented numerically for analyzing arbitrary structures of rectangular dielectric waveguides. The comparison of the results with those available in literature are favorable. With the numerical results for various waveguide structures, the method is demonstrated to be efficient and capable of solving very complex structures such as coupled rib waveguides and coupled channel waveguides.

ISSN:0920-5071    

DOI:10.1163/156939391X00031

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The concept of polarimetry in active remote sensing is extended to passive remote sensing. The potential use of the third and fourth Stokes parameters U and V, which play an important role in polarimetric active remote sensing, is demonstrated for passive remote sensing. It is shown that, by the use of the reciprocity principle, the polarimetric parameters of passive remote sensing can be obtained through the solution of the associated direct scattering problem. These ideas are applied to study polarimetric passive remote sensing of periodic surfaces. The solution of the direct scattering problem is obtained by an integral equation formulation which involves evaluation of periodic Green's functions and normal derivative of those on the surface. Rapid evaluation of the slowly convergent series associated with these functions is observed to be critical for the feasibility of the method. New formulas, which are rapidly convergent, are derived for the calculation of these series. The study has shown that the brightness temperature of the Stokes parameter U can be significant in passive remote sensing. Values as high as 50 K are observed for certain configurations.

ISSN:0920-5071    

DOI:10.1163/156939391X00040

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Resonant frequencies and unloaded Q's of hybrid modes on cylindrical dielectric resonators in conducting enclosures are studied. The formulation uses the mode matching technique, and includes axially symmetric (TE0mand/or TM0m), as well as axially non-symmetric hybrid (HEnm,) modes which could exist in dielectric loaded waveguides. The structures analyzed can simulate resonators on ground plane backed or suspended substrates. Losses in the conducting walls, substrates, and the dielectric material, and stored energy in the general resonator are obtained. Mode amplitudes determined from the solution of the boundary value problem by mode matching are used to rigorously compute the unloaded Q's of the resonators. Numerical results in the millimeter wave range and in C-band are presented. These results include unloaded Q's and mode charts of dielectric resonators on ground plane backed and suspended substrate structures. From these results, methods for improving the unloaded Q's and mode's separation are explored. Experimental results are presented which verify the accuracy of the model used and the numerical computations.

ISSN:0920-5071    

DOI:10.1163/156939391X00059

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A connection algorithm is presented for analyzing the electromagnetic scattering from arbitrarily shaped open cavities. This approach allows different sections of the cavity to be analyzed independently of one another. The aperture admittance matrix representation of each region is generated using the boundary-integral method. Applying the concept of input and load admittance, a connection algorithm is developed to cascade all the aperture admittance matrices together to form the aperture admittance matrix of the entire cavity. Finally, the aperture electric field can be found from the generalized network formulation and the backscattered field can be determined. Numerical examples are presented to demonstrate the advantages of this algorithm that include modeling flexibility and reduced computational resources.

ISSN:0920-5071    

DOI:10.1163/156939391X00068

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

New basis functions are used for the problem of solving the surface current on a conducting plate by the method of moments. Pyramidal functions adopted from the finite element method are geometrically flexible. Entire domain trigonometrical functions offer the advantage of computing the tangential electric field everywhere on the surface of the plate, because the surface charge densities are continuous. In this way the error can be estimated in the domain of the operator.

ISSN:0920-5071    

DOI:10.1163/156939391X00077

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00086

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00095

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor